1. Field of the Invention
The present invention relates to a vertical type low pressure chemical vapor deposition apparatus for fabricating a semiconductor device, and more particularly, to a vertical type low pressure chemical vapor deposition apparatus for fabricating a semiconductor device in which sealing leaks through the closely contacted surfaces between a manifold and a cap, due to byproducts such as quartz powder, can be prevented.
2. Description of the Related Art
A conventional vertical type low pressure chemical vapor deposition apparatus for fabricating a semiconductor device supplies a predetermined gas that is necessary to form a thin film on a wafer into a process chamber at high temperature and low pressure. The conventional vertical type low-pressure chemical vapor deposition apparatus for fabricating a semiconductor device comprises a vertical type heating chamber and a boat that is received in the vertical type heating chamber.
The heating chamber comprises a process chamber consisting of an inner tube and an outer tube spaced apart from the inner tube by a predetermined distance, and a manifold coupled to a lower portion of the process chamber. The manifold is generally made of stainless steel, flange-coupled at the upper portion thereof with a lower portion of the outer tube, and coupled with a lower portion of the inner tube at an inner side thereof that is vertically extended. The outer tube is provided at an external side thereof with a heater for heating the internal side of the heating chamber.
The boat is loaded with a large number of wafers that are stacked in a vertical direction, and the boat is moved up and down into the heating chamber by an elevator. As illustrated in FIG. 1, the manifold 20 is in close surface contact with the cap 60 of the boat that is inserted into the process chamber, thereby sealing the process chamber. That is, the manifold 20 is in tight horizontal surface contact with the cap 60 at the bottom surface thereof, and an O-ring 70 is tightly inserted between the manifold 20 and the cap 60, thereby maintaining airtight characteristics in the process chamber, as illustrated in FIG. 1A.
As the boat repeatedly moves in and out of the process chamber a great number of times, the contact surfaces between the manifold 20, and the cap 60 and the O-ring 70, are worn away, damaged and changed, thereby resulting in air leaks in the process chamber. To solve such a problem, U.S. Pat. No. 5,578,132 discloses an apparatus and a method for improving the structure of the process chamber. However, in addition to the problem caused by the O-ring, there is another problem in that since the inner tube, the outer tube, and the boat are made of quartz, they crack due to repeated changes in temperature, pressure, reactive gas, etc. in the process chamber over a span of many hours, so that a byproduct such as quartz powder is created and comes apart from the inner and outer tubes. As a result, the byproduct is accumulated on the upper portion of the cap 60 and collected between the contact surfaces of the manifold 20 and the cap 60, thereby damaging sealing between the manifold 20 and the cap 60, as illustrated in FIG. 2.
In other words, a byproduct such as quartz powder comes off from the inner and outer tubes, and a part of the byproduct accumulates near the O-ring between the contact surfaces of the manifold 20 and the cap 60, thereby creating leaks in the airtight sealing. As a result, a constant vacuum pressure in the process chamber cannot be maintained while the boat is loaded into the process chamber and the processes are performed. Consequently, thin films on a wafer cannot be formed properly, so that inferior products are created and productivity decreases.
The present invention is therefore directed to a low pressure chemical vapor deposition apparatus of vertical type for fabricating semiconductor devices, which substantially overcomes one or more of the problems due to the limitations and disadvantages of the related art.
To solve the aforementioned problems, it is an object of the present invention to provide a vertical type chemical vapor deposition apparatus by which byproducts can be prevented from accumulating on the contact surfaces between a cap and a manifold, thereby increasing reliability of processing.
It is another object of the present invention to provide a vertical-type chemical vapor deposition apparatus by which the number of inferior wafers produced can be reduced, and productivity can be increased.
In order to achieve the above objects, the vertical type chemical vapor deposition apparatus includes a process chamber having a cylindrical inner tube and a cap shaped outer tube surrounding and apart from the inner tube; a manifold, coupled with lower portions of the inner tube and the outer tube, having a lower portion tapered at an inclination angle; a heater, provided at an outer side of the outer tube, that heats an inner side of the process chamber to a process temperature; a boat that is movable into and out of the process chamber through the manifold as driven by an elevator, the boat being vertically loaded with a plurality of wafers; a cap, fixed to the elevator and coupled to a lower portion of the boat, having a portion that is contactable with the manifold and that is tapered at a same inclination angle as the lower portion of the manifold; and an O-ring inserted into the portion of the cap that is contactable with the manifold.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.